1) Book now...just sit down, figure out what you want to do and book the flight before the fares spike. Kayak.com has weekly and daily fare alerts. Sign up by plugging in where you want to go and how much you want to pay and they will email you when the fare meets (or beats) your target price.
2) On Kayak.com you can also check the airfare history by clicking on "chart" view after searching for a fare. In some cases it may be much cheaper to fly over New Years weekend than over Christmas.
3) Check alternative airports! It might be a little further away but well worth the savings.
4) If you book your holiday ticket through Delta, sign up for the '
tickets for life ' sweepstakes first for a chance to win 2.5 million miles, then book your flight.
Nice. I've never used kayak.com, I'll check it out for my possible new years trip. Thanks.